Depend on what you want, these days the sofware gives you so much control that sometimes you can lose yourself in the process, yet the steps are as follow: selct your subject, get as many reference as you can, model it in 3D, clean it, unwrap it for texturing, make the textures, put the textures in the 3d model, test the textures, light it and finally render it, of course you have to think in the backround for the image, that of course is another whole process, in all, in average about a week, but as I said, depends on your subject and of course in your skill, this model in particular is very easy to do because is made of a lot of simple "primitives", spheres, cylinders, etc.